Postoperative Gravity Line-Hip Axis Offset as a Substantial Risk Factor for Mechanical Failure After Adult Spinal...

Area of Science:

• Spine surgery
• Orthopedics
• Biomechanical engineering

Background:

• Mechanical failure (MF) is a significant complication following adult spinal deformity (ASD) correction surgery.
• Understanding and preventing MF remains a challenge for surgeons.
• Global sagittal balance, represented by the gravity line (GL), is a key parameter in spinal alignment.

Purpose of the Study:

• To evaluate the postoperative gravity line-hip axis (GL-HA) offset as a predictor of mechanical failure (MF) in patients who underwent adult spinal deformity (ASD) surgery.
• To identify critical thresholds for GL-HA offset associated with MF.
• To inform surgical strategies for reducing MF after ASD correction.

Main Methods:

• Retrospective analysis of consecutive patients undergoing initial ASD surgery at a single academic center.
• Evaluation of demographics, operative details, spinopelvic parameters, global sagittal balance, and Scoliosis Research Society-22 scores.
• Logistic regression analysis to determine the correlation between postoperative GL-HA offset and MF.

Main Results:

• Thirty patients experienced MF, while 35 did not, with no significant differences in baseline characteristics.
• Postoperative GL-HA offset was significantly correlated with MF (odds ratio: 11.0, P < .0001).
• A GL-HA offset cutoff of 49.3 mm was identified as a critical risk factor for MF.

Conclusions:

• Postoperative GL-HA offset is a substantial risk factor for mechanical failure after adult spinal deformity surgery.
• Surgical correction aiming for a GL-HA offset greater than 5 cm is significantly associated with increased risk of MF.
• Optimal surgical outcomes in ASD correction require positioning the gravity line close to the hip axis.